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Zwitterionic Phosphorus Ylide Adducts of Boron‐Bridged ansa ‐Zirconocene Complexes as Precatalysts for Olefin Polymerization
Author(s) -
Shapiro Pamela J.,
Jiang Feilong,
Jin Xiaoping,
Twamley Brendan,
Patton Jasson T.,
Rheingold Arnold L.
Publication year - 2004
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200300932
Subject(s) - chemistry , cyclopentadienyl complex , zirconium , polymerization , adduct , boron , tacticity , medicinal chemistry , polymer chemistry , catalysis , inorganic chemistry , organic chemistry , polymer
Methylenetriphenylphosphorane was coordinated to the boron of phenylborylidene‐bridged bis(cyclopentadienyl)‐ and bis(2‐Me,4‐Ph‐indenyl)zirconium dichloride to form zwitterionic ansa ‐zirconocene complexes. The cyclopentadienyl complex 2 , when activated with MAO, exhibits remarkable polymerization activity that is more than an order of magnitude greater than that of a related amidoborylidene‐bridged complex as well as the commercially important precatalyst [Cp′−SiMe 2 − N − t Bu]TiCl 2 (Cp′ = C 5 Me 4 ). The zwitterionic bis(2‐Me,4‐Ph‐indenyl)zirconium dichloride species is isolated as a mixture of rac and meso isomers 4 − 6 . The propylene polymerization efficiency of the isomer mixture activated by MAO is greater than that of a related silylene bridged system at 70 and 85 °C; however, the activity of the zwitterionic system decreased with further increase in temperature. The high level of isotactic triads (63.6%) and pentads (52.4%) in the polypropylene formed by 4 − 6 indicates that the rac isomer is the most active precatalyst of the mixture. The molecular structures of 2 and the rac bis‐indenylzirconium isomer 4 and one of the meso isomers 5 are described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)